I think he'll return to Vienna. He seemed to like the place, and it's been upgraded to a 500, so a good swap for Valencia, and the timing seems to work nicely too. He might want to play something before Shanghai, but that could depend on how Davis Cup goes. I think he'll be ready for a break after that.
That's what I thought as well. There are 3 weeks between the DC tie and the start of Shanghai, so Andy may well want to play Beijing or Tokyo so he doesn't go into Shanghai - where he can gain a lot of points - 'cold'. Of course there's Shenzhen the week before Beijing/Tokyo which he could opt for and not play either of the 500s, though that seems a little unlikely, but he is defending there.
All about balancing rest/recovery and playing in the latter part of the year. Smart scheduling must be a tricky thing to get right.